1. Field of the Invention
The present invention is broadly concerned with an improved method and apparatus for the incorporation of added liquid or meltable solid components into heterogeneous materials. More particularly, the invention pertains to such methods and apparatus wherein the components and other starting materials are continuously passed in serial order through an extruder and a sonolation device.
2. Description of the Prior Art
The commercial-scale production of emulsified products is a common problem encountered by industry. For example, it is sometimes necessary to incorporate oils or lipids into heterogeneous materials such as grains. One way of accomplishing this is to use relatively large quantities of emulsifiers. While this does yield effective emulsions, emulsifiers are very expensive. In another example, it is also sometimes necessary to add liquid ingredients to highly viscous gel or paste products such as toothpastes. In the past, it has generally been necessary to produce such products in a batchwise manner, because of the difficulty of insuring product uniformity.
Extruders are well known devices adapted for production of an almost limitless number of products such as animal or livestock feeds, starches and pastas. Extruders include an elongated barrel having an inlet and a spaced outlet, with one or more elongated, axially rotatable flighted screws located within the barrel for moving materials along the barrel. The outlet end of the barrel is normally equipped with a restricted orifice die serving to create back pressure within the barrel and to form the extrudate into a desired shape. In many instances, extruders are used to simultaneously cook and form materials, and in such cases generate elevated temperatures and pressures. In other cases, extruders can be used at relatively low or even ambient temperatures as forming devices.
Sonolation devices have also been proposed in the past for assisting in the mixing of materials. Such sonolation devices are in the form of elongated, tubular units having an internal orifice and a tunable, blade-like member adjacent the orifice. In use, materials passing through the sonolation device are subjected to intense acoustic vibrations which tend to break up discrete liquid droplets within the material to achieve a more uniform and emulsified final product. Sonolation devices are described in U.S. Pat. Nos. 3,176,964 and 5,854,336, both of which are incorporated by reference herein.